Integrating device



N wy

United States Patent INTEGRATING DEVICE John B. Breazeale, Solana Beach,Calif., assignor to Bill Jack Scientific Instrument Co., Solana Beach,Calif., a corporation of California Application April 16, 1956, SerialNo. 578,512

Claims. (Cl. 340-178) The present invention relates to computing devicesand, more particularly, to a method and device for integrating afunction which varies with time and which is represented by a current orvoltage signal.

An important object of the present invention is to provide a new andimproved high precision integrating device for obtaining the integral ofa current or voltage input signal with respect to time, and whichresponds rapidly to changes in the input signal.

Another object is to provide a new and improved high precisionintegrating device from which both first and second integrals withrespect to time of an input electrical signal can be obtained.

A further object of the present invention is to provide a new andimproved integrating device for obtaining an integral of an electricalsignal, which device is capable of performing the integrating functionregardless of the polarity or the changes in polarity of the inputsignal.

Yet another object of the present invention is to provide a new andimproved integrating device in which the input signal to be integratedenergizes the field coils of a torquer for applying a torque to a rotorwhich is proportional to the input signal and in which the angularvelocity of the rotor is measured to determine the first integral andthe total angular rotation is measured to obtain the second integral ofthe input signal with respect to time.

A further object of the present invention is to provide a new andimproved integrating device in which the angular velocity of a rotor isindicative of the first integral of the input signal with respect totime and wherein the torque applied to the rotor is proportional to themagnitude of the input signal.

Further objects and advantages of the present invention will be apparentfrom the following description of the preferred embodiment made withreference to the accompanying drawings, the disclosure of which,including all constructions and arrangements shown therein, and theadvantages apparent therefrom and inherent therein, whether or notexpressly described hereinafter, forms a part of this specification anddescription of the preferred embodiment, and wherein:

Figure 1 is a view, chiefly diagrammatic, showing an integrating deviceembodying the present invention; and

Figure 2 is a block circuit diagram showing the components of thetorquer of the device of Figure 1.

The present invention contemplates the provision of a novel integratingdevice wherein a rotor has a torque applied thereto which isproportional to an input signal to be integrated with respect to timeand wherein the angular velocity and the total angle of rotation of therotor provide an indication of the first and second integralsrespectively, the rotor preferably being magnetically suspended so as tominimize the errors due to friction.

Referring to the drawings, the preferred embodiment shown thereincomprises a rotor magnetically suspended between electromagnets 11, 12.The electromagnets 11, 12 are comprised of electric coils 14, 15,respectively, wound on spaced coaxial cylindrical cores 16.

The rotor 10 includes a cylindrical member 18 coaxial with the cores 16and a disc 20 fixed to the cylindrical member 18 and coaxial therewith.Preferably the disc 20 is at approximately the midpoint of the length ofthe member 18. To maintain the rotor 10 in a predetermined axialposition between the electromagnets 11, 12 a pair of coaxial andcoplanar sensing coils 22, 23 is provided on each side of the disc 20,the coils lying in planes parallel to and coaxial with the disc.exciting coils and respectively induce currents in the coplanar coils22, the induced currents in the coils 22 depending on the position ofthe disc 20 relativeto the coils. If the disc shifts axially from itsnormal center position between the pairs of coils on the opposite sidesthereof, the induced current in one of the coils 22 will in-'v creaseWhile the induced current in the other coil 22 will decrease. The coils22 are connected to a control servomechanism 25 for controlling thecurrents flowing in the coils 14, 15 of the electromagnets in accordancewith the induced currents in the coils 22. The control servomechanism 25is responsive to the currents induced in the coils 22 to reduce theenergization of the electromagnet toward which the disc 20 moves and toincrease the energization of the other electromagnet. The particularconstruction of the servo-mechanism does not, per se, form a part ofthis invention and therefore has not been shown or described in detail.Suitable servo-mechanisms are well known to those skilled in the art anda servomechanism similar to that shown and described in copendingapplication Serial No. 544,954, now Patent No. 2,838,974, filed November4, 1955, by myself and others as joint inventors, is suitable for usewith the present invention. Amplifiers 26 are preferably providedbetween the servo-mechanism and each electromagnet 11, 12.

The rotor 10 is rotated by means of a torquer 27 having field coils 28,29 inductively coupled with an annular member 30 carried by the outerperiphery of the disc 20. Energization of the field coils 28, 29 createsa torque tending to rotate the rotor 10. The electrical signal to beintegrated is applied to the input of the torquer and the torque appliedto the rotor 10 is proportional to the magnitude of the input signal.

Torquers suitable for use with the present invention are known to thoseskilled in the art. If desired a torquer of the type shown in Figure 2may be utilized. In the torquer of Figure 2, the direct current inputwhich is to be integrated is connected to the field coil 28 through achopper 31 for periodically interrupting the direct current inputsignal, the output of the chopper being amplified by an alternatingcurrent amplifier 32. The chopper 31 has the same frequency as, andoperates in phase with, an alternating current source 33 for energizingthe field coil 29. The alternating source 33 is connected to' the fieldcoil '29 through a phase shifting circuit 34 so that the currents in thetorquer coils are out of phase with each other. Since the torque appliedto the rotor 10 is the product of the currents in the field coils 28,29'

and since the current in field coil 29 is constant and that in fieldcoil 28 proportional to the input signal, the torque applied to therotor is proportional to the input signal. When a torque is applied tothe rotor 10, the motion of rotor 10 may be described by the followingdifferential equation:

where T is the torque applied to the rotor, I is the moment of inertiaof the rotor about its axis, and 0 is the angle through which the rotorhas turned. Since the torque is directly proportional to the voltage ofthe input signal the above equation may be written as:

Patented Oct. 6, 1959 The coils 23 are.

3 where V is the input voltage. K is a proportionality constantdependent on the geometry and construction of the torquer and rotor.This constant K may be defined as the torque, in dyne-cm., produced onthe. rotor by the applicationof one volt to the input terminals of thetorquer 27. Taking the first integral en 7 r fvdt Since i i dt be seenthat I v -f fVdt dt and that the second integral of V with respect totime can be obtainedby measuring the total angle of rotation of therotor 10.

The cylindrical member 18 of the rotor 10 carries a mirror 35, and alight source or lamp 36 has its rays directed so as to be reflected bythe mirror into a photoelectric cell 37 when the mirror is in apredetermined position during its rotational movement. Each flash oflight creates an electrical pulse so that the angular velocity oftherotor 10 may be obtained by measuring the frequency of the pulses andthe total angular 'rotation obtained by counting the pulses. Formeasuring the angular velocity and total angular movement of the rotor10, the output of the photoelectric cell is amplified and connected toan oscilloscope and pulse counter respectively.

The magnetically suspended rotor is preferably suspended within a vacuumenclosure, not shown in the drawings. a

While the rotor 10 has been described as, and preferably is,magnetically suspended, certain features of the invention are applicableto non-magnetically suspended rotors. Additionally, other means thanthat described may be provided for measuring the angle velocity andtotal angular movement of the rotor.

It can now be seen that the present invention provides a new andimproved, high precision integrating device preferably operable toobtain first and second integrals of an input signal and while thepreferred embodiment thereof has been described in detail, it is myintention to cover all modifications and constructions and arrangementswhich fall within the ability of those skilled in the art and the scopeof the appended claims.

What I claim is:

1. A device for obtaining the integral of an electrical input signalcomprising a rotor, means for magnetically suspending said rotorincluding spaced electromagnets and control means responsive to changesin axial position of said rotor for controlling the energization of saidelectromagnets to maintain the rotor in a predetermined position inspace free from friction, a single means for imparting a torque to saidrotor proportional to the magnitude of the input signal, and means formeasuring the angular velocity of said rotor.

2. A device for obtaining the integral of an electrical input signalcomprising a rotor, means for magnetically suspending said rotorincluding spaced electromagnets and control means responsive to changesin axial position of said rotor for controlling the energization of saidelectromagnets to maintain the rotor in a predetermined position inspace free fromfriction, a single means for imparting a torque to saidrotor proportional to the magnitude of the input signal, and means formeasuring the angular velocity and total angle of rotation of saidrotor. a I a 3. A device for obtaining the integral of an electricalinput signal comprising a rotor, means for magnetically suspending saidrotor including spaced electromagnets and control means responsive tochanges in axial position of said rotor for controlling the energizationof said electromagnets to maintain the rotor in a predetermined positionin space free from friction, a single means for imparting a torque tosaid rotor proportional to the magnitude of the input signal, means formeasuring the angular velocity of said rotor comprising a reflectingsurface rotatable with said rotor, means for directing light on saidsurface at it moves through a' predetermined position to produce areflection, and photoelectric means responsive to said reflection.

4. A device for obtaining the integral of an electrical input signalcomprising a rotor, means for magnetically suspending said rotorincluding spaced electromagnets and control means responsive to changesin axial position of said rotor for controlling the energization of saidelectromagnets to maintain the rotor in a predetermined position inspace free from friction, a single means for imparting a torque to saidrotor proportional to the magnitude of the input signal, means formeasuring the angular velocity and total angle of rotation of said rotorcomprising a reflecting surface rotatable with said rotor,

means for directing light on said surface as it moves through apredetermined position to produce a reflection, and photoelectric meansresponsive to said reflection.

5. In a device for obtaining first andsecond integrals of an electricalinput signal, first and second spaced coaxial electromagnets, a cylinderrotor member coaxial with .said electromagnets and magneticallysuspended in space thereby, a disc carried by and coaxial with saidrotor, means responsive to axial movements of said disc for controllingthe energization of said electromagnets 'to maintain said disc and rotormember in a predetermined axial position, a single torque producingmeans responsive to an electrical input signal for applying a torque tosaid rotor which torque is proportional to the input signal, areflecting surface carried by said rotor, means for directing light rayson said surface as it passes through a predetermined position to producea reflection, and photoelectric means responsive to said reflection tomeasure the angular velocity and total angular rotation of said rotor.

. References Cited in the file of this patent UNITED STATES PATENTS1,721,375 DeKonig July 16, 1929 1,857,593 Hill May 10, 1932 2,007,220Smith July 9, 1935 2,398,238 vMcNatt Apr. 9, 1946 2,485,888 Jordan Oct.25, 1949 2,513,537 Williams July 4, 1950 2,566,221 Lovell Aug. 28, 19512,602,837 Foster July 8, 1952 2,691,306 Beams Oct. 12, 1954 g

